Manufacturers just can't leave Android alone. When they build Android devices, they've got to customize. There's Samsung's TouchWiz, Motorola's MotoBlur, HTC's Sense, and others. These customizations have come to be known as skins.

Skins are a touchy subject. Enthusiasts howl about how much better a phone would be if it didn't even have a skin—if it just used stock Android, straight from Google. Our readers scream about them every time we write about a new Android phone. We grumble about them as loud as anybody. It's enough to make you wonder just why the hell manufacturers keep using skins at all. So, we asked them.

What Is a Skin?

When Google releases the latest version of Android, raw and naked to the world, phone manufacturers customize that software for their phones and tablets. The OS alteration—the skin—changes the look of the software and how it performs. But let's get one thing straight: To manufacturers, "skin" is a dirty word.

"This is a contentious topic," says Drew Bamford, HTC's AVP of User Experience. "I wouldn't call it a 'skin', really, in the sense that a skin is something thin. HTC Sense is actually quite an extensive and deep experience. It goes way beyond the homescreen or any of the other parts of the UI."

All of the manufacturers prefer the term "third-party UI." Okay, fine.

Why Do Skins Third-Party UIs Exist?

The basic answer any manufacturer will offer is that a skin enhances the user experience.

For HTC, skins began as a way to make phones way more usable. Back in 2007, Windows Mobile was made for use with a stylus. HTC needed to alter the UI so the HTC Touch could be navigated with finger gestures. That evolved into putting user content front and center in the UI for the HTC Diamond, and much of that experience was ported over to Sense on the HTC Hero, which was the first Android device to sport a third-party UI. Highlighting personal content is still HTC's top priority for Sense, but so is adding functionality. Sense lets you dial directly out of the calendar, run a keypad search in the dialer, and the camera has features like a self-portrait countdown timer.

Samsung's mission with TouchWiz is both to clarify the Android interface and to beef up the features. Power controls are embedded in the notification panel, providing quick access to commonly used settings without having to switch out of a task. There's automatic face-tagging in photos, and better Enterprise integration. Then there are features you wish were included in Android at its core—one setting checks to see if you're still looking at the phone; if not, the screen shuts off. And there's support for an SD card, which we haven't seen in stock Android since the Nexus One.

From Motorola's perspective, there are two main reasons manufacturers go to customization. "The first is if the platform you're building on is simply under-developed, and there's a lot more that has to be done," according to Punit Soni, Motorola Mobility's VP of Product Management. "And the second thing is to push your own brand identity so that you're different from the other manufacturers." Motorola's focus is on the former, which has meant adding less and less as Android matures.

How Have Skins Evolved?

The skins have evolved alongside Android. Between Android versions 2.3 (Gingerbread) and 4.0 (Ice Cream Sandwich), there was a significant shift in the way the OS looked and functioned. Android 4.1 (Jelly Bean) honed it in even further, making things extremely fast, simple, and smooth—there was such a dramatic improvement between 4.0 and 4.1, in fact, many thought third-party UIs would cease to exist. They haven't. But they've changed again.

Motorola is on one extreme. MotoBlur was the name of Motorola's UI that launched in 2010. It was thrashed by critics. Now, Motorola doesn't even use the MotoBlur brand name. Some of the customization still exists, but as Android has gotten better, Motorola's skin has been pared back from what it once was. It's not as necessary, the thinking goes, because Google has adapted Android itself to deliver most of things that customers want. "I think that we should minimize customization to Android," said Motorola's Soni. "Reinventing the wheel may not be the best use of our resources."

He is for adding software to fix holes in Android, like making settings more accessible. But overall, his philosophy is to look to the hardware first. See how that works with Android already. Then, if you have to build software on top of that to make it work better, so be it. Maybe this approach has something to do with the fact that Google acquired Motorola Mobility (or that Soni worked for Google first).

HTC Sense has gone in a similar direction, from very heavy-handed to something much more resembling stock. "The shift was driven by our customers—by listening to them about how they felt about Sense 3," says HTC's Bamford. "A lot of the feedback we got, frankly, was that it felt a bit overwrought. We kind over over-designed it, adding too many animated transitions and too much detail. It was extraneous." Now, HTC focuses on the user's content, and tries to make the UI fade into the background.

In contrast, Samsung has gone the other direction. It strives for mass appeal of its Galaxy devices (e.g. the Galaxy S III, the Galaxy Note II) by adding unique functionality. The more the better. It positively loads TouchWiz with every bell and whistle it can fit, from camera functionality to expanded voice controls in hopes of reaching a broader audience.

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The irony of Samsung's quest is that in an attempt to make something that appeals to the everyman, they've actually made things vastly more complex. Menus are more legible, but they're obscured by the sheer volume of features. It's enough for even hardcore geeks to get lost. A small example. Most phones running ICS or later have a clearly marked, dedicated key for multitasking, whereas Samsung devices require a long-press on the unmarked home button. A double-click on that same button brings up S-Voice. Most new users I've talked to had no idea. It's a small thing, but it's representative of the design philosophy: rather than making things more intuitive, TouchWiz relies on memorized behaviors.

Are These Changes OK With Google?

Google created Android to be an open platform, so it's customizable by nature. Google doesn't want to stop that. In fact, it's quite the opposite. According to Nick DiCarlo, Samsung's VP of Product Planning and Marketing, "Google has induced a system where some of the world's largest companies—the biggest handset manufacturer and a bunch of other really big ones—are also investing huge money behind their ecosystem. It's a really powerful, and honestly pretty brilliant business model."

It makes sense. Google can employ several hundred people to develop Android at a base level, but huge companies like Samsung may devote thousands of people to improve upon it. When we interviewed Matias Duarte, Director of Android User Experience at Google, he expressed great enthusiasm for third-party UIs. "We realize that the customizability of these skins, while some of them are bad, some of them are very good, and some of them are things the customers actually prefer to stock Android or to other skins. That's one of the things that makes the Android ecosystem work: it provides so much choice."

What About the Carriers?

Beyond the manufacturers and Google, the wireless providers also have a motivation to offer a phone with a distinct skin—they want to carry a line of products that create unique benefits, says HTC's Bamford. "If they were forced to carry five Android phones from different manufacturers with the same UI, it's going to be a lot harder for them to explain to the customer why they would want one over the other."

But the carrier's requirements go deeper than product differentiation. "Even before the new software load shows up, we have a set of requirements that the OEM [original equipment manufacturer] is building toward," says T-Mobile's Jason Young. "How quickly can you get to certain tasks? What type of onscreen keyboard experience is it? We require that from the homescreen to the camera it should take X seconds. Or from homescreen to the browser being open it should take X seconds." T-Mobile has a half-dozen product requirement documents that cover these standards, as do all other carriers.

A carrier can direct a phone maker to deliver on its requirements, or, like Spint, work with Google directly. The goal there is to have Google build these feature into to Android's next release. Whatever Sprint doesn't get through Google is passed on as a requirement to the manufacturers. These carriers' needs go beyond simple ease-of-use.

"Ultimately, because (the carriers) are the ones you pay the bill to and buy the phone from, they own the customer, right? That's their view, that's basically our view," says Samsung's DiCarlo. "And so they want to create service adoption within their system." That translates to adding carrier-specific applications and services—the pre-installed features that some reviews call "bloatware." Carriers present it a value-adding benefit, and sometimes that's true. But ultimately, a skin is another opportunity to get a customer further tied in to a carrier's ecosystem.

Don't Skins Delay Updates?

Here's one of the criticisms most frequently leveled at third-party UIs: It's the skins' fault that some phones take so long to get updated to the latest version of Android. The truth is, the bulk of that delay happens before the skin is ever applied.

When Google releases an update to Android, it's in a raw form. It must be developed and tweaked to work with each phone's hardware, software and drivers, so that everything plays nicely together under the new OS. How long it takes depends on the size and scope of the changes from Google. Everything is tested, then retested. It can take an OEM roughly 2 months just to get the OS update from Google in good enough shape to deliver to a carrier. That timeline depends on the complexity of the upgrade, and how that particular device is prioritized by the OEM.

"Even if we did no customization, I'm not sure that the process would be much faster, to be honest," says HTC's Bamford. "There's quite a bit of discussion and negotiation between HTC and our carrier partners before we get to the point where we can release an update."

After the OEM signs off, then the carrier begins its own exhaustive testing. "When we release a new product to carriers, we can have it running in our labs for six months before it's released by the carrier. It can take a long time," says Samsung's DiCarlo.

So, Consumers Prefer Pure Android, Right?

That's the thing. So many phone reviews you read will say, "Ugh... the skin..." Every comment on that post may agree. But that doesn't necessarily reflect the broader reality of the situation.

The blogosphere is very vocal, but it's a vocal minority. Outside the internet echo chamber, in the real world, the vast majority of consumers do not know what a skin (let alone a "third-party UI") is. Most don't know what version of Android their phone runs. And they don't they care. They just want a phone that works well. The community of tech enthusiasts may find this hard to accept, but it's true.

"For a small minority of people buying Android phones, the Nexus program is very popular," HTC's Bamford says. "I think there's appeal for those people for what's considered a more 'pure' Android experience. But actually I think it's quite a small segment. I don't think the Nexus phones are actually selling in very high volume."

DiCarlo said the same thing of Samsung's Galaxy S III, which runs TouchWiz and is almost certainly the most popular Android phone to date. "We think enthusiasts will find things to love about it, but that the enthusiast's mom will love it, too."

Bamford shared the sentiment. "The enthusiast market is important to HTC. That's our core. Those are our original users. So we don't want to abandon those people. But we're also trying to adapt to a much broader consumer market that, frankly, has much different needs. We're trying to balance the needs of the enthusiast with those of more typical consumers."

When all is said and done, no one device can please everyone. That's part of the wide-open Android strategy. If you don't like one phone, you have a ton of others to choose from. Love it or hate it, Android skins are here to stay.